A disk drive for a computer commonly is placed in an enclosure in order to, for example, protect or cool the disk drive. An enclosure commonly includes one or more external electrical connectors that are connected inside the enclosure by a cable to the disk drive. An enclosure may be constructed to be placed in rack equipment or may be constructed to be placed on a desktop.
Advances in disk drive technology that provide greater storage density and access speeds also are accompanied by problems caused by higher power consumption and revolutions per minute of the disk drive. These problems include increased heat and increased noise. Techniques for reducing noise tend to be thermally insulating and thus increase heat around a disk drive. Techniques for reducing heat by convection, such as rotating fans, tend to create noise. The use of conduction to dissipate heat, such as by a heat sink, often is ineffective to adequately cool the disk drive, because integrated circuits in a disk drive generally do not have a heat conduction path from within the disk drive to a heat sink.
Other reliability problems are associated with the cable that connects the disk drive to the external connector of the enclosure. For example, the impedance of a cable is affected by its proximity to both devices within the enclosure and the enclosure itself. Because a cable may be placed in many locations within an enclosure, the impedance of the cable can vary significantly from enclosure to enclosure. Single-ended small computer systems interface (SCSI) signals and low voltage differential (LVD) signals are particularly sensitive to such variations in impedance. The cable also can become loose after manufacturing, or can be installed incorrectly.
Another reliability problem arises when data is striped, i.e., a data word is divided and written in parallel, to a set of disk drives. Such a set of disk drives is called a stripe set. After data is stored on a stripe set, the order of the disks in the stripe set must be maintained in order to maintain data integrity. The exact physical arrangement of the disk drive enclosures for the stripe set, for example in a stack, ideally would be maintained in order to ensure data integrity. Some users actually resort to using adhesive tape or other physical measures to bind the set of disk drive enclosures together.
These problems are particularly undesirable in computing environments where high reliability and low noise are expected, such as in professional multimedia authoring studios. Computer systems in such environments typically use a large amount of disk capacity, particularly if the disks are used for storing audio and video information. The large number of disks both creates a significant amount of noise and increases concern for reliability.